This web page was produced as an assignment for an
undergraduate course at Davidson College.

Cells interact with the
extracellular environment by cell-surface receptors which recognize and
bind with antigen. Specifically, the T and B lymphocytes that have
bound their particular antigen produce a series of intricate
intracellular signals that respond to the stimulus. This process of
transmitting, and often amplifying a signal, through the cell is known
as signal transduction (Campbell, 1996). One major pathway of signal
transduction occurs by way of Ras. Ras is a small protein that is
activated by GTP and is thus in the class of G proteins (Janeway et
al., 1999). The Ras family consists numerous different Ras
proteins, however of most importance are the human H-, K-, and N-Ras
proteins (Boguski et al., 1993)

Figure 1-
The back bone of the small G protein Ras. Typical Ras
molecules contain approximately 190 residues (Boguski et al.,
1993). This image is used with permission from Dr. Raymond
Mosteller at the University of Southern California Keck School of Medicine
(http://www-hsc.usc.edu/~rmostell/).

OVERVIEW

The small G protein Ras regulates many aspects
of cell growth and differentiation and for this reason has been
under intense study in the past decade. In fact recent discoveries
link the Ras superfamily to tumorigenicicy (Boguski et al., 1993). Ras is
found in two states: the active state when GTP is bound and the
inactive state, when GDP is bound. Tumorigenicity is prevellant when
mutations allow Ras to remain activated state, thus relaying a signal for
cell growth (Bourne et al., 1990).